The present invention relates to a refrigeration system including a two-stage linear compressor with dual-opposed pistons, and more particularly to a control system for operating the linear compressor in an economizer cycle.
In refrigeration systems, such as those used in cooling display cases of refrigeration merchandisers, it is necessary to maintain a constant temperature in the display cases to ensure the quality and condition of the stored commodity. Many factors demand varying the cooling loads on evaporators cooling the display cases. Therefore, selective operation of the compressor of the refrigeration system at different cooling capacities corresponds to the cooling demand of the evaporators. In refrigeration systems utilizing existing scroll and screw compressors, an economizer cycle is used to increase the refrigeration capacity and improve efficiency of the refrigeration system. In the economizer cycle of existing scroll and screw compressors, gas pockets in the compressor create a second “piston” as mechanical elements of the compressor proceed through the compression process.
Further, scroll compressors use oil for operation, which results in inefficient performance due to oil film on evaporator and condenser surfaces, requires the use of expensive oil management components, and increases the installation cost of the refrigeration system. Scroll compressors are operable with an economizer, however, efficiency is compromised because the volume ratio is fixed. Some refrigeration systems utilize a linear compressor, which provides variable capacity control of the refrigeration system.